This invention relates to a single-stage oilless screw compressor system which is suitable for use as a source of air supply in fields in which a clean gas (air) is required, such as a food industry, a testing and measuring instrument manufacturing industry, a painting and a press for semiconductor manufacturing apparatus.
An oilless screw compressor system is known as a system for producing a clean air or clean gas having no oil incorporated therein. In this known system, for example, disclosed in U.S. Pat. No. 3,367,562, a gas has its pressure raised by two-stage compression, that is, the gas is compressed by means of a low pressure stage compressor to about 3 kgf/cm.sup.2 (gauge pressure) and is cooled by an intermediate cooler and then the gas is compressed again by means of a high pressure stage compressor to a predetermined level between 7 and 8 kgf/cm.sup.2 (gauge pressure) and is cooled again by an aftercooler.
The system of the prior art for supplying a clean gas is of a two-stage compression type not of a single-stage compression. Even if a single-stage oilless screw compressor is combined with the two-stage compressor system, it would be impossible to eliminate obnoxious effects of high temperature because the temperature of the discharged gas of the single-stage compression oilless screw compressor would exceed 300.degree. C. In a known system, no means has been provided for eliminating defects which would be experienced due to the discharged has having a high temperature.